The formation of low-resistance junctions between reaggregated normal and cancer cells in culture will be studied with electrophysiological, dye-passing, and electron-microscopic techniques. We will define the stages of formation between Novikoff hepatoma cells, to determine the types of molecules involved in the formation process, and test the generality of the findings using other culture cells. We will also investigate the possible role of low-resistance junctions in control of cell proliferation by studying junctional permeability to cyclic nucleotides, the changes in junctional permeability and structure during the cell cycle, the junctional effects of growth-modulating agents, and the correlation between junctional area and rate of cell proliferation.